Let me gather a little information kluc lkae:
1. Kaeya and Diluc like apple cider.
2. The favorite animal of the two is the owl.
3. Diluc knows how to cook, play instruments and also knows archery so I assume Kaeya knows a bit of this too

4. While Kaeya likes wine (death of the AfterNoon), Diluc dislikes it.
5. Kaeya hates grape juice and Diluc loves it.
6. Kaeya's favorite food is mushroom skewers, while Diluc's is "once upon a time in Mondstadt..."

7. Diluc's birthday is on April 30 and Kaeya's birthday is on November 30.
8. Kaeya is a one-handed swordsman and Diluc uses a claymore that he can even manipulate with one hand

Kaeya's constellation is Pavo Ocellus and Diluc's is Noctua.
10. Diluc got the vision from his around 10 years old, while Kaeya got it almost as an adult.

11. Kaeya is from Khaenri'ah, he was left by his biological father when he was little (it is believed that he was 7 or 8 years old)

12. It is believed that the current age of Diluc is 22 years (information from the manhua), but that of Kaeya is not, it may be a year or two younger than Diluc

Plus: Although, in Kaeya's character story, it says that he came to the Winery around a decade